如何在循环中呈现HTML5画布 [英] How to render HTML5 canvas within a loop

问题描述

我正在做以下事情：

我正在运行一个for循环，每次我得到一个新信息并希望在帆布。
问题是画布是在循环结束后绘制的，我看不到没有动画。
如果我介入调试或使用警报消息，它将立即绘制到画布。我该怎么办？

I'm running through a for loop and each time I get a new information and want to draw it on the canvas. The problem is that the canvas is being drawn just after the loop finish, and I can't see no animation. If I step in with debug, or with alert messages, it will draw to the canvas immediatly. How can I do it?

这是我的代码，你可以看到我已经尝试过多种方式的setTimeout但是没有用。

Here is my code, as you can see I've already tried with setTimeout in multiple ways but didn't worked.

for(var i=0;i<1000; i ++)
    {
        addLines(ga.getBestCreature());   // This method draw on the canvas 

        setTimeout(function() {
        ga.startEvolution(1);       // This method change the best creature
        }, 10);   
    }

投掷方法：

function addLines(best) {

    if(!best) {
        return;
    }
    var global_path = best.data;

    redraw(); // Clear off the canvas

    var cityA;
    var cityB;
    for (var i = 0; i < (global_path.length - 1); i++) {

        cityA = ga.cities[global_path[i]];
        cityB = ga.cities[global_path[i+1]];

        ctx.moveTo(cityA.x,cityA.y);
        ctx.lineTo(cityB.x,cityB.y);
        ctx.stroke();
    }
}

任何想法??

更新：在被建议使用requestAnimationFrame之后，我发布了类似的内容。这是最好的approuch吗？
我正在更新点击事件中名为'run'的全局变量

Update: After was advised to use the requestAnimationFrame, I've came out with something like this. Is this the best approuch? I'm updating a global variable called 'run' on click events

var run = 0;
function animate() {

    if(run > 0) {
        ga.startEvolution(1);
        run--;
    }

addLines(ga.getBestCreature());
    requestAnimationFrame(animate);
}

animate();

推荐答案

你最好的办法是分开关注：动画片循环连续运行，并且，每次[你]获得一个新信息，更新您的场景描述，它将在显示准备就绪后立即绘制。

Your best take is to separate concerns : have an animation loop continuously running, and, "each time [you] get a new information", update your scene description, it will draw as soon as the display is ready.

这是第一个非常简单的演示：这里的'新信息'是用户点击。

So a first very simple demo : here the 'new information' is a user click.

var cv = document.getElementById('cv');
var ctx = cv.getContext('2d');
var cvWidth = cv.width;
var cvHeight = cv.height;

// Simple scene description : an array of colored rects
var everyObject = [
  [60, 70, 30, 30, 'yellow']
];

// animation : always running loop.

function animate() {
  // call again next time we can draw
  requestAnimationFrame(animate);
  // clear canvas
  ctx.clearRect(0, 0, cvWidth, cvHeight);
  // draw everything
  everyObject.forEach(function(o) {
    ctx.fillStyle = o[4];
    ctx.fillRect(o[0], o[1], o[2], o[3]);
  });
  // 
  ctx.fillStyle = '#000';
  ctx.fillText('click to add random rects', 10, 10);
}

animate();


// click handler to add random rects
window.addEventListener('click', function() {
  addRandRect();
});

function addRandRect() {
  var randColor = Math.random() > 0.5 ? 'blue' : 'red';
  everyObject.push([Math.random() * cvWidth, Math.random() * cvHeight, 10 + Math.random() * 40, 10 + Math.random() * 40, randColor]);
}

<canvas id='cv' width=400 height=200></canvas>

现在，如果你想要某种动画，或者使用setTimeOut的简单版本是：

Now if you want some kind of animation, or a simple version using setTimeOut would be :

var cv = document.getElementById('cv');
var ctx = cv.getContext('2d');
var cvWidth = cv.width;
var cvHeight = cv.height;

// Simple scene description : an array of colored rects
var everyObject = [
  [60, 70, 30, 30, 'yellow']
];

// animation : always running loop.

function animate() {
  // call again next time we can draw
  requestAnimationFrame(animate);
  // clear canvas
  ctx.clearRect(0, 0, cvWidth, cvHeight);
  // draw everything
  everyObject.forEach(function(o) {
    ctx.fillStyle = o[4];
    ctx.fillRect(o[0], o[1], o[2], o[3]);
  });
  // 
  ctx.fillStyle = '#000';
  ctx.fillText('click to add 4 random rects with a delay', 10, 10);
}

animate();


// click handler to add random rects
window.addEventListener('click', function() {
  addRandRect();
  setTimeout(addRandRect, 300);
  setTimeout(addRandRect, 600);
  setTimeout(addRandRect, 900);
});

function addRandRect() {
  var randColor = Math.random() > 0.5 ? 'blue' : 'red';
  everyObject.push([Math.random() * cvWidth, Math.random() * cvHeight, 10 + Math.random() * 40, 10 + Math.random() * 40, randColor]);
}

  <canvas id='cv' width=400 height=200></canvas>

（顺便说一句，我在这里写了关于动画的方式如有兴趣： http://codepen.io/gamealchemist/post/animationcanvas1 ）

(By the way i wrote about animation here if interested : http://codepen.io/gamealchemist/post/animationcanvas1 )

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